Caltrans crews will again close lanes on Interstate 5 through Sacramento this week for emergency repairs after two sections of the freeway crumbled last month and potholes damaged several dozen vehicles. The night closures will allow the state to finish replacing 400 concrete slabs along a 10-mile stretch that investigators have determined are at risk of failing. The work, which could take several weeks, will occur on both sides of the freeway from the southern edge of downtown to Pocket Road. That work will require lane closures as far north as J Street downtown, Caltrans said. The closures will begin at 9 p.m. nightly from Wednesday through Saturday. The lanes will reopen at 5 a.m. on weekdays and 7 a.m. on weekends. The state already has replaced 280 concrete slabs in the last two weeks and has 120 to go as part of an emergency $6.5 million fix.